getTimer problems

hi…

i have been searching google and yahoo for hours on this one with no success grrr

i have an .fla, which loads goes to different frames in the timeline according to the download speed of the user. i understand how it should work… start timer > upload file > stop timer > calculate download speed - easy?

so what is this simple code im missing to find the download speed? from my fruitless searching, the only relevant code i could find, is this:
Code:

var time1 = getTimer();

targetClip.loadMovie(“example.swf”);
targetClip.onLoad = function()
{
var time2 = getTimer();
var totalTime = (time2 - time1)/1000;
var fileSize = targetClip.getBytesTotal();
var connectionSpeed = (fileSize/totalTime); // Bytes per second. Multiply by 8 to get bits per second.
}

… but i have test this, which gives an undefined property error grrr… so what is the actionscript 3, to find the value of the download speed?

please help if you can

thanks